Serum angiotensin-converting enzyme levels in patients with pigeon-breeder's disease.

The serum concentration of angiotensin-converting enzyme is frequently elevated in individuals with active sarcoidosis. The enzyme is presumably actively synthesized by the epithelioid and giant cells of the granuloma. Hypersensitivity pneumonitis, resulting from the inhalation of antigens from pigeons by susceptible individuals, is associated with the development of a granulomatous interstitial and alveolar infiltrate in the pulmonary parenchyma. Because the clinical and pathologic presentation may mimic that of sarcoidosis, we compared the serum levels of angiotensin-converting enzyme in these two diseases. The concentration of angiotensin-converting enzyme is not elevated in individuals with active hypersensitivity pneumonitis, in contrast to its frequent elevation in sarcoidosis. We suggest that the granulomatous response in hypersensitivity pneumonitis may differ at a biochemical level from that of sarcoidosis, since the synthesis of angiotensin-converting enzyme does not appear to be increased.